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![Nathan Chancellor](/assets/img/avatar_default.png)
When building with Clang + -Wtautological-pointer-compare:
drivers/cpufreq/s3c64xx-cpufreq.c:152:6: warning: comparison of array
's3c64xx_freq_table' equal to a null pointer is always false
[-Wtautological-pointer-compare]
if (s3c64xx_freq_table == NULL) {
^~~~~~~~~~~~~~~~~~ ~~~~
1 warning generated.
The definition of s3c64xx_freq_table is surrounded by an ifdef
directive for CONFIG_CPU_S3C6410, which is always true for this driver
because it depends on it in drivers/cpufreq/Kconfig.arm (and if it
weren't, there would be a build error because s3c64xx_freq_table would
not be a defined symbol).
Resolve this warning by removing the unnecessary NULL check because it
is always false as Clang notes. While we are at it, remove the
unnecessary ifdef conditional because it is always true.
Fixes: b3748ddd80
("[ARM] S3C64XX: Initial support for DVFS")
Link: https://github.com/ClangBuiltLinux/linux/issues/748
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
208 lines
4.9 KiB
C
208 lines
4.9 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Copyright 2009 Wolfson Microelectronics plc
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*
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* S3C64xx CPUfreq Support
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*/
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#define pr_fmt(fmt) "cpufreq: " fmt
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#include <linux/kernel.h>
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#include <linux/types.h>
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#include <linux/init.h>
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#include <linux/cpufreq.h>
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#include <linux/clk.h>
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#include <linux/err.h>
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#include <linux/regulator/consumer.h>
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#include <linux/module.h>
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static struct regulator *vddarm;
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static unsigned long regulator_latency;
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struct s3c64xx_dvfs {
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unsigned int vddarm_min;
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unsigned int vddarm_max;
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};
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static struct s3c64xx_dvfs s3c64xx_dvfs_table[] = {
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[0] = { 1000000, 1150000 },
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[1] = { 1050000, 1150000 },
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[2] = { 1100000, 1150000 },
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[3] = { 1200000, 1350000 },
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[4] = { 1300000, 1350000 },
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};
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static struct cpufreq_frequency_table s3c64xx_freq_table[] = {
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{ 0, 0, 66000 },
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{ 0, 0, 100000 },
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{ 0, 0, 133000 },
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{ 0, 1, 200000 },
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{ 0, 1, 222000 },
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{ 0, 1, 266000 },
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{ 0, 2, 333000 },
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{ 0, 2, 400000 },
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{ 0, 2, 532000 },
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{ 0, 2, 533000 },
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{ 0, 3, 667000 },
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{ 0, 4, 800000 },
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{ 0, 0, CPUFREQ_TABLE_END },
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};
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static int s3c64xx_cpufreq_set_target(struct cpufreq_policy *policy,
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unsigned int index)
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{
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struct s3c64xx_dvfs *dvfs;
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unsigned int old_freq, new_freq;
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int ret;
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old_freq = clk_get_rate(policy->clk) / 1000;
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new_freq = s3c64xx_freq_table[index].frequency;
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dvfs = &s3c64xx_dvfs_table[s3c64xx_freq_table[index].driver_data];
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#ifdef CONFIG_REGULATOR
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if (vddarm && new_freq > old_freq) {
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ret = regulator_set_voltage(vddarm,
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dvfs->vddarm_min,
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dvfs->vddarm_max);
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if (ret != 0) {
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pr_err("Failed to set VDDARM for %dkHz: %d\n",
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new_freq, ret);
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return ret;
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}
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}
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#endif
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ret = clk_set_rate(policy->clk, new_freq * 1000);
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if (ret < 0) {
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pr_err("Failed to set rate %dkHz: %d\n",
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new_freq, ret);
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return ret;
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}
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#ifdef CONFIG_REGULATOR
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if (vddarm && new_freq < old_freq) {
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ret = regulator_set_voltage(vddarm,
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dvfs->vddarm_min,
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dvfs->vddarm_max);
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if (ret != 0) {
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pr_err("Failed to set VDDARM for %dkHz: %d\n",
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new_freq, ret);
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if (clk_set_rate(policy->clk, old_freq * 1000) < 0)
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pr_err("Failed to restore original clock rate\n");
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return ret;
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}
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}
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#endif
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pr_debug("Set actual frequency %lukHz\n",
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clk_get_rate(policy->clk) / 1000);
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return 0;
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}
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#ifdef CONFIG_REGULATOR
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static void s3c64xx_cpufreq_config_regulator(void)
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{
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int count, v, i, found;
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struct cpufreq_frequency_table *freq;
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struct s3c64xx_dvfs *dvfs;
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count = regulator_count_voltages(vddarm);
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if (count < 0) {
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pr_err("Unable to check supported voltages\n");
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}
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if (!count)
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goto out;
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cpufreq_for_each_valid_entry(freq, s3c64xx_freq_table) {
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dvfs = &s3c64xx_dvfs_table[freq->driver_data];
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found = 0;
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for (i = 0; i < count; i++) {
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v = regulator_list_voltage(vddarm, i);
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if (v >= dvfs->vddarm_min && v <= dvfs->vddarm_max)
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found = 1;
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}
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if (!found) {
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pr_debug("%dkHz unsupported by regulator\n",
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freq->frequency);
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freq->frequency = CPUFREQ_ENTRY_INVALID;
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}
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}
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out:
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/* Guess based on having to do an I2C/SPI write; in future we
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* will be able to query the regulator performance here. */
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regulator_latency = 1 * 1000 * 1000;
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}
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#endif
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static int s3c64xx_cpufreq_driver_init(struct cpufreq_policy *policy)
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{
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struct cpufreq_frequency_table *freq;
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if (policy->cpu != 0)
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return -EINVAL;
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policy->clk = clk_get(NULL, "armclk");
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if (IS_ERR(policy->clk)) {
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pr_err("Unable to obtain ARMCLK: %ld\n",
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PTR_ERR(policy->clk));
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return PTR_ERR(policy->clk);
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}
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#ifdef CONFIG_REGULATOR
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vddarm = regulator_get(NULL, "vddarm");
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if (IS_ERR(vddarm)) {
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pr_err("Failed to obtain VDDARM: %ld\n", PTR_ERR(vddarm));
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pr_err("Only frequency scaling available\n");
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vddarm = NULL;
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} else {
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s3c64xx_cpufreq_config_regulator();
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}
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#endif
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cpufreq_for_each_entry(freq, s3c64xx_freq_table) {
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unsigned long r;
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/* Check for frequencies we can generate */
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r = clk_round_rate(policy->clk, freq->frequency * 1000);
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r /= 1000;
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if (r != freq->frequency) {
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pr_debug("%dkHz unsupported by clock\n",
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freq->frequency);
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freq->frequency = CPUFREQ_ENTRY_INVALID;
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}
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/* If we have no regulator then assume startup
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* frequency is the maximum we can support. */
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if (!vddarm && freq->frequency > clk_get_rate(policy->clk) / 1000)
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freq->frequency = CPUFREQ_ENTRY_INVALID;
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}
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/* Datasheet says PLL stabalisation time (if we were to use
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* the PLLs, which we don't currently) is ~300us worst case,
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* but add some fudge.
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*/
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cpufreq_generic_init(policy, s3c64xx_freq_table,
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(500 * 1000) + regulator_latency);
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return 0;
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}
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static struct cpufreq_driver s3c64xx_cpufreq_driver = {
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.flags = CPUFREQ_NEED_INITIAL_FREQ_CHECK,
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.verify = cpufreq_generic_frequency_table_verify,
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.target_index = s3c64xx_cpufreq_set_target,
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.get = cpufreq_generic_get,
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.init = s3c64xx_cpufreq_driver_init,
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.name = "s3c",
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};
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static int __init s3c64xx_cpufreq_init(void)
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{
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return cpufreq_register_driver(&s3c64xx_cpufreq_driver);
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}
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module_init(s3c64xx_cpufreq_init);
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